While a steel frame work method (hereinafter referred to as a first prior art method) has been mainly employed as a construction method for a low-rise building of one to three stories in the prior art, a steel house construction method has recently been prevalent. In this regard, the steel house is defined as a building of a steel panel structure composed of frame members made of thin lightweight section steel and construction surface members or braces. This construction method is referred to as a second prior art method hereinafter.
An example of a single-storied building constructed by the first prior art method (the steel frame work method) is illustrated in FIGS. 16 to 18. Individual footings 1 and a floor (a stall) 2 are constructed from concrete.
Columns 3 made of steel frame are facilitated on the individual footings 1 and wall substrates 4 are provided. Beams 5 of H-shaped steel are mounted to the upper ends of the columns 3, and girders 5a are bridged between the left and right beams 5, by which beams and girders a roof 6 is supported. In this regard, in FIGS. 17 and 18, reference numeral 4a denotes a wall and 7 denotes a doorway (e.g., an opening).
The features of the first example are as follows. A material cost for the roof is low; the number of parts is low; manufacturing is easy; site work is easy in that one day is sufficient for erecting a building for a convenience store or the like; the opening is freely prepared (if necessary, studs may be used in accordance with a width of the opening); and only cutting of the constituent members is needed. However, drawbacks thereof are that the precision of execution of work is liable to vary; LGS (light-gage steel) is necessary as a substrate for finishing the wall; and site work needs two days.
FIGS. 19 to 21 illustrate another example of a single-storied building for a convenience store or the like constructed by the second prior art method (the steel house (SH) method). A continuous footing 8 and a floor (a stall) 2 are constructed from concrete, and wall frame panels 9 made of thin light-gauge section steel are stood on the continuous footing 8.
As shown in FIG. 21, the wall frame panel 9 is formed by standing vertical frame members 11 of thin light-gauge section steel on a lower frame member 10 of thin light-gauge section steel, placing an upper frame member 12 of thin light-gauge section steel on the vertical frame members 11, and fixing a construction surface member 13 to the respective frame members with drill screws 19. Hereinafter, the product obtained by fixing the construction surface member 13 to the respective frame members is referred to as an SH panel 9.
Further, a truss 14 of thin light-gauge section steel (hereinafter referred to as an SH truss) is assembled to be supported by the wall frame panel 9, and a roof 6 is supported by the SH truss 14. In FIG. 20(A), reference numeral 15 denotes a relatively large opening (e.g., a window or a doorway).
As shown in FIG. 20(A), both ends of a lintel 16 are fixed to the vertical frame members 11 via lintel brackets 17 above the opening 15 for transmitting a vertical load from the roof to the wall frame panel 9. FIGS. 20(B) and 20(C) illustrate examples of the lintel 16, in which lipped channels 16a of thin steel sheet are opposed to each other and the outside thereof is reinforced with a reinforcement channel(s) 18.
FIGS. 20(D) and 20(E) illustrate another example, in which opposite flanges of the lintel bracket 17 of a U-shaped thin steel plate as seen in a plan view are brought into contact with lateral sides of an end of the lintel 16 and fixed to each other with drill screws 19, and a web is brought into contact with a back side of the vertical frame members 11 and fixed to each other with drill screws 19.
In such a manner, the steel house is constructed by using the frame members of thin light-gauge section steel as main frame elements, to which wood frame members are partially combined or a surface member of plywood is used as a construction surface member if necessary.
The frame member of thin light-gauge section steel is formed by shaping a thin steel sheet of approximately 1 mm thick, through roll-forming, to be a channel, a lipped channel or a box so that a width or others thereof is matched with a predetermined specification.
A further example of a frame construction according to the second prior art method is illustrated in FIGS. 22 to 25. A plurality of vertical frame members 11 are provided from lower frame members 10 at a distance between the adjacent ones thereof, and the upper ends of the respective vertical frame members 11 are coupled by upper frame members 12.
Wall frame panels (force-resisting wall panels) 9 are formed by attaching construction surface members 13 (see FIGS. 24 and 25) or braces to the wall frame members constructed by the lower frame members 10, the vertical frame members 11 and the upper frame members 12. Openings 15 such as a doorway 7 or a window 7a are formed in the building.
Side beams 5b and end beams 5c are supported by the upper frame members 12 of the wall frame panel (force-resisting wall panel) 9 so that both the beams are combined to form a rectangle. A plurality of beams 5c of various lengths are provided in parallel to the side at a predetermined distance.
Opposite ends of the longer beam 5d are coupled to the front and rear end beams 5c via brackets 20, while one end of the shorter beam 5d is coupled to the front or rear end beam 5c and the other end thereof is coupled to a girder 5a via brackets 11, respectively.
One end of the girder 5a is coupled to the side beam 5b, while the other end thereof is coupled to the longer beam 5d via the brackets 20, respectively. A floor panel 2 is constructed by covering the beams 5d with the construction surface members 13 of plywood or the like.
In FIG. 22, reference numeral 5e denotes an end beam in the floor opening, 5f denotes a side beam in the opening, 20a denotes a beam bracket, and 20b denotes a cleat.
In the above-mentioned building according to the SH method, as there are no vertical frame members 11 in the opening 15 such as a doorway 7 or a window 7a, no columns exist in the opening 15, for supporting a vertical load from the upper portion of the building such as a roof, resulting in the deterioration of strength in the opening 15.
Therefore, it may be necessary to reinforce the upper portion above the opening 15. Thus, the lintel 16 is provided above the opening 15.
As shown in FIG. 22, an upper frame member 12 and a lintel frame member 16b are provided above and beneath the lintel 16 of the window 7a, respectively.
Upper frame members 12a of the opening are provided between the lintel frame member 16b and upper frame member 16c of the window, and opposite ends of the lintel 16 are attached to lintel receiving members 16d via the lintel brackets 17, and vertical frame members 11a for attaching the lintel brackets are coupled to the vertical frame members 11 at ends of the force-resisting wall 9 by drill screws 19. Reference numeral 7b denotes a window base, 7c denotes a window base, and 10a denotes a lower frame member of the opening.
FIG. 24 schematically illustrates an opening 15 of a building formed of a ground floor portion 36 constructed by the SH method and a second floor portion 37 placed on the former, and FIG. 25 illustrates a section taken along a line A-A in FIG. 24. Each of the drawings shows a connection structure between the lintel 16, the end beam 5c and the beam 5d. An end of the beam 5d having the bracket 20 is coupled to the end beam 5c made of thin light-gauge section steel.
The bracket 20 is formed by cutting a lipped channel of thin light-gauge section steel into short pieces and disposing it so that the channel portion is in the vertical direction. The lintel 16 arranged beneath the end beam 5c and coupled thereto by drill screws is formed by opposing the lipped thin light-gauge channels 16a to each other and fixing the upper and lower sides thereof by connection frame members 16d. 
According to the second prior art method (the steel house (SH) method), a skeleton is constructed of the force-resisting wall panels (SH panels) constructed by the wall frame members which are formed by assembling the frame members of thin light-gauge section steel by using the drill screws and are coupled to the construction surface members also by using the drill screws. The merit thereof is that the thin light-gauge section steel necessitates no welding, and is easily cut and drilled, as well as it also being light in weight and capable of being manually conveyed, whereby the working efficiency is high and the manufacturing cost is low.
The merit of the force-resisting wall panel (SH panel) is that the accuracy of the product is stable and prefabrication of the panel is possible, whereby the execution of work becomes easy due to the shortening of construction period and the maintenance of panel accuracy.
For example, in a single-storied building for a convenience store, the period of erection is half of a day, and in a two or three storied building of approximately 99 to 132 m2, the period of erection is two days. Accordingly, this construction method is economical in the field of low-rise buildings.
The second prior art method (steel house (SH) method), however, has the following drawbacks. For example, in the building for a convenience store or the like, it is required that a large opening is formed on the wall surface and the number of columns is reduced to as small as possible to ensure a large space.
That is, in the building, when a roof of large span is constructed in correspondence to a required large span of several meters or longer, as the cross-section of the thin light-gauge section steel is small, the strength thereof is too weak to support a load from the roof solely by the end members. Thereby, it is necessary to construct a roof truss consisting of a plurality of members.
In the above-mentioned roof truss, the number of parts increases, the number of portions to be coupled by drill screws or bolts increases, and an area of the side surface wall increases, which are uneconomical because of the increase in man-hours. Also, when it is required to guarantee a large room space, the second prior art method could not respond to a case in which the span between supports of the roof is as large as ten or more meters.
In the low-rise building of 2 to 3 stories constructed by thin light-gauge section steel, as an opening such as a doorway or a window formed on the wall surface lacks the strength for supporting the vertical load applied from above, the lintel is provided in the upper portion of the opening to distribute the vertical load, applied to the opening from above, to the opposite vertical frames of the force-resisting wall panel.
The lintel is required to have a strength capable of withstanding a vertical load, from above, such as the load of a roof or a floor. Thereby, the lintel preferably uses a member in which a plurality of thin light-gauge section steel pieces are combined to result in the complexity of the manufacture and construction of the lintel.
Further, when the opposite ends of the lintel are attached to the side ends of the force-resisting wall panel disposed on both sides of the opening, the attachment of the lintel to the peripheral members becomes complex in relation to complexity in the structure of the lintel. Further, the height of the opening (i.e., reference h provided in FIG. 24) can be restricted due to the existence of the lintel.